1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to a receiving multiview camera parameters for a stereoscopic image, and transmitting multiview camera parameters for a stereoscopic image, and more particularly, to a method and apparatus for efficiently receiving or transmitting multiview camera parameters by redefining multiview camera parameters for a stereoscopic image.
2. Description of the Related Art
Camera parameters for a stereoscopic image are used in various image processing applications including disparity estimation using an Epipolar line constraint and stereoscopic image rectification. Camera parameters are also used to generate low fatigue parameters or fatigue reduction algorithms by analogizing environmental conditions when an image is obtained. However, a standard format for the storage of camera parameters for a stereoscopic image is yet to be developed.
FIG. 1 illustrates a relationship between a world coordinate system 110 and a camera coordinate system 120. The world coordinate system 110 has an XW axis, a YW axis, and a ZW axis, and the camera coordinate system 120 has an XC axis, a YC axis, and a ZC axis. An origin of the world coordinate system 110 is spaced apart from an origin of the camera coordinate system 120 by a distance t, and the camera coordinate system 120 is rotated with respect to the world coordinate system 110 by an angle R. An arbitrary point P is expressed as PW in the world coordinate system 110, and expressed as PC in the camera coordinate system 120. A relationship between the world coordinate system 110 and the camera coordinate system 120 will now be explained with reference to Equation 1.MC=R−1MW−R−1t  (1)where MC and MW are arbitrary points in the coordinate systems 110 and 120, R is a rotation matrix of the camera coordinate system 120 based on the world coordinate system 110, and t is a distance between the world coordinate system 110 and the camera coordinate system 120.
FIG. 2A illustrates a relationship between a camera coordinate system 210 and a two-dimensional image coordinate system 220.
The camera coordinate system 210 has an XC axis, a YC axis, and a ZC axis, and the two-dimensional image coordinate system 220 is displayed by a real display device. An object with coordinates (X, Y, Z) in the camera coordinate system 210 is imaged at a point (x, y, f) in the two-dimensional image coordinate system 220. A relationship between the coordinates (X, Y, Z) and (x, y, f) is given by Equation 2, and x and y are expressed by Equation 3.f:Z=x:X f:Z=y:Y  (2).x=f×X/Z y=f×Y/Z  (3).
FIG. 2B illustrates a relationship between a camera coordinate system 210 and an arbitrary point in an image.
Reference numeral 220 denotes a coordinate system of a scene which is imaged in the camera coordinate system 210, and reference numeral 230 denotes an image coordinate system 230.
It is assumed that a pixel pitch in the coordinate system 220 is (SX, SY), a center point of the coordinate system 220 is imaged at a point (oX, oY) of the image coordinate system 230, and a point (x, y) of the coordinate system 220 is imaged at a point (xim, yim) of the image coordinate system 230. A relationship between the image coordinate system 230 and the camera coordinate system 210 is expressed byx=−(xim−oX)×sX y=−(yim−oY)×sY  (4).
A point which is imaged in the image coordinate system 230 by an arbitrary point in the camera coordinate system 210 using Equations 3 and 4 is determined byxim=−(f/sX)×(X/Z)+OX yim=−(f/sY)×(Y/Z)+OY  (5).
The relationship between the camera coordinate system 210 and the image coordinate system 230 is expressed in matrix form by Equations 6 through 8.s×m=A×MC  (6).
Equation 7 is derived from Equations 1 and 6.s×m=A×(R−1MW−R−1t)  (7).
A matrix A for a focal length, an aspect ratio of an image, and a center point (oX, oY) which are intrinsic parameters is given by
                    A        =                              (                                                                                                      -                      f                                        /                                          s                      X                                                                                        0                                                                      o                    X                                                                                                0                                                                                            -                      f                                        /                                          s                      Y                                                                                                            o                    Y                                                                                                0                                                  0                                                  1                                                      )                    .                                    (        8        )            
Accordingly, when camera parameters are transmitted, a rotation angle between coordinate systems and a translation should be transmitted as extrinsic parameters, and a focal length, an aspect ratio of an image, and a center point should be transmitted as intrinsic parameters.